IRepublican Congressman Tom Cotton, who is challenging U.S. Sen. Mark Pryor, D-Ark., in the November election, raised $2.28 million over the past three months his campaign said Monday. (ASSOCIATED PRESS / Danny Johnston)

LITTLE ROCK (AP) — U.S. Rep. Tom Cotton raised $2.28 million over the past three months in his bid to unseat Democratic U.S. Sen. Mark Pryor, the Republican's campaign said Monday, outpacing the two-term Arkansas incumbent as their nationally watched race grows more expensive and heated.

Cotton's fundraising haul bests the $1.5 million that Pryor announced raising during the same period. Tuesday is the deadline for campaigns to report their quarterly fundraising numbers for the period that ended June 30.

Cotton's campaign did not say how much it spent during the quarter or how much cash it had on hand. Pryor's campaign last week announced it had $4.1 million cash on hand, but didn't say how much it spent during the three-month period.

Cotton's campaign said the fundraising means it will be able to continue criticizing Pryor as too closely aligned with President Barack Obama.

"Our continued fundraising strength will allow us to highlight Senator Pryor's lockstep support for President Obama's agenda, including his votes for Obamacare, bailouts, and other job-killing policies," Cotton spokesman David Ray said in a statement released by the campaign.

Pryor's campaign announced his quarterly fundraising amount Friday afternoon and said the figures showed the Democratic lawmaker was well-positioned to win a third term. Pryor's campaign on Monday dismissed Cotton's numbers, accusing GOP rival of representing out of state groups more than Arkansas.

"Frankly, we're surprised it took this long for someone as ambitious as Congressman Cotton to rally his out-of-state billionaires behind his otherwise troubled candidacy," spokesman Erik Dorey said in a statement released by the campaign.

Pryor is the only Democrat in Arkansas' congressional delegation and was first elected in 2002. He was re-elected in 2008 without any Republican opposition. Cotton was elected in 2012 to represent south Arkansas' 4th Congressional District and launched his bid to challenge Pryor last August.

The two campaigns and outside groups have spent millions on the race, with television ads from both sides blanketing Arkansas' airways. The increasingly expensive race in Arkansas is closely watched because Republicans need a net gain of six seats in November to capture majority control of the Senate. Top-tier GOP targets are the Republican-leaning Southern states — Arkansas, Louisiana and North Carolina — where Obama is unpopular and incumbent Democratic senators are struggling to hold onto their seats.